Pyramidal Fabrics Having Multi-Lobe Filament Yarns and Method for Erosion Control

ABSTRACT

A pyramidal geotextile fabric comprising two sets of multi-lobe filament yarns interwoven in substantially perpendicular direction to each other, each of the multi-lobe filament yarns having pre-determined, different heat shrinkage characteristics such that, upon heating, the fabric forms a three-dimensional, cuspated profile. A method of stabilizing soil and reinforcing vegetation comprises the steps of placing a three-dimensional, high-profile woven fabric into soil, wherein the fabric comprises two sets of multi-lobe filament yarns interwoven in substantially perpendicular direction to each other, each of the multi-lobe filament yarns having pre-determined, different heat shrinkage characteristics such that, upon heating, the fabric forms a three-dimensional, cuspated profile; securing the fabric to the ground; and, distributing soil and seed onto the fabric such that the section of ground is quickly revegetated and thereby protected from further erosion.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/251,855, now U.S. Pat. No. 10/066,354, filed Apr. 14, 2014, which isa continuation of U.S. patent application Ser. No. 13/267,593, now U.S.Pat. No. 8,747,995, filed Oct. 6, 2011, which is a continuation of U.S.patent application Ser. No. 11/297,022, filed Dec. 8, 2005, now U.S.Pat. No. 8,043,689, which is a continuation-in-part of Ser. No.11/142,412, filed Jun. 2, 2005, now abandoned, that claims priority ofU.S. Provisional Application Ser. No. 60/584,881, filed Jun. 29, 2004,whose disclosures are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates generally to three-dimensional, high-profile,woven geotextile structures and their method for use in soil retentionand stabilization and vegetative reinforcement. More particularly, thisinvention relates to a generally planar, single-layered homogeneousfabric woven from cross-sectional multi-lobe filament yarns havingdifferent heat shrinkage characteristics such that, when heated, thefabric forms a thick three-dimensional, cuspated profile. The multi-lobefilament yarns have a relatively high tensile strength and a relativelyhigh modulus at 10 percent elongation so as to provide a fabric which isgreater in strength and more dimensionally stable than otherthree-dimensional, woven geotextile structures. Such a geotextile fabricis suitable for use on slopes, ditches and other embankments andsurfaces where erosion control, soil stabilization and/or vegetativereinforcement may be necessary. The homogeneous, single-component natureof the fabric promotes easier handling and minimizes failure points,while offering a thick, strong and dimensionally stable product uponinstallation.

Known geotextile products having been used for erosion protection andcontrol include pyramidal fabrics and turf reinforcement mats (TRM's).The latter are typically fabricated in one of the following three ways:(1) polymer monofilament or natural organic fibers are stitch bondedtogether; (2) polymer monofilament can be fused with netting or (3)polymer monofilaments are woven into erosion control structures. Theformer include high profile, woven geotextile fabrics.

Woven fabrics having heat-shrinkable yarns incorporated therein are wellknown. For example, at least three patents to B. H. Foster in the early1950's (U.S. Pat. Nos. 2,627,644, 2,635,648, and 2,771,661) and one toMcCord in 1956 (U.S. Pat. No. 2,757,434) use heat-shrinkable yarns alongwith non-heat-shrinkable yarns to make honeycombed, puffed and/orcorrugated fabrics for use in bedding, clothing and the like.

In addition, woven fabrics having the same or similar general cuspatedprofile or “honeycomb” type weave configuration as the present inventionare known in the art and are used as tower packing and/or as theseparation medium in mist eliminators. For instance, Pedersen U.S. Pat.No. 4,002,596 relates to a fluid treating medium through which fluid maypass for removing particulate material from the fluid. The material usedis comprised of at least two sets of strands interleaved together in aparticular configuration to each other so that the strands extending inone direction are generally straight while the strands extending inanother direction are geometrically arranged so as to provide a fabrichaving a cuspated configuration or profile. The fabric of the presentinvention is similar in profile except it may bend the strands of yarnin both directions.

Also of major importance to the use of fabrics in soil design andperformance are weight, strength, and modulus. It is a combination ofthese properties, including thickness, which determines whether ageotextile fabric will be suitable for use in soil retention andstabilization as well as turf reinforcement. Desirably, a fabric havinga typical tensile strength of at least about 4000×3000 pounds per foot(warp x fill, respectively) as determined by the American Society forTesting and Materials (ASTM) Standard Test Method D6818, a modulus of atleast about 10000 pounds per foot determined by ASTM D6818 at 10 percentelongation, is necessary to provide soil stabilization and erosioncontrol on slopes, embankments, subgrades and veneer layers in placessuch as landfills. While some mattings and other similar structureshave, heretofore, been used to aid in soil retention or erosion control,most of these structures have been generally ineffective in providingtrue stability and reinforcement for the soil. In fact, most of theprior art structures have employed generally straight yarns in at leastone direction, are not heat-shrinkable, and/or have filaments which aremelt-bonded together so as to cause failure points to exist with respectto the bonding of the fabric.

For example, Daimler et al. U.S. Pat. No. 3,934,421 discloses a mattingcomprising a plurality of continuous amorphous synthetic thermoplasticfilaments which are bonded together at their intersections and can beused for the ground stabilization of road beds.

Murhling et al. U.S. Pat. No. 4,002,034 is directed toward amulti-layered matting for inhibiting the erosion of an embankment arounda body of water, the layer closest to the water having less pore spaceand thinner fibers than the layers away from the water.

Bronner U.S. Pat. No. 4,329,392 discloses a hydraulic engineeringmatting for inhibiting rearrangement of soil particles comprising alayer of melt-spun synthetic polymer filaments bonded at their points ofintersection, a filter layer of fine fibers bonded thereto, and a thirdlayer interdispersed therethrough.

Ter Burg et al. U.S. Pat. No. 4,421,439 discloses a supporting fabric ormatting for use on embankments of roads, dikes, and the like. The fabricgenerally includes straight yarns in both the warp and weft directionswith binder yarns extending in the warp direction and woven around thestraight yarns of the weft direction. However, these yams do not impartstrength to the straight yams.

Leach U.S. Pat. No. 4,472,086 is directed toward a geotextile fabric forerosion control having, uncrimped synthetic threads in both the warp andfilling directions and a known yarn stitch bonding the warp and fillingthreads together.

Finally, a commercially known high-profile structure generally used forsoil retention and erosion control which does employ heat-shrinkableyams, but not in a single layer, is disclosed in Stancliffe et al. U.S.Pat. No. 4,762,581. This patent relates to high-profile structures orcomposites which are noted to be useful as carpet underlay andmattresses as well as embankment stabilization and drainage. Thesestructures are believed to be commercially sold under the trade name,Tensar, and are available from Netlon Limited of Mill Hill, England.

However, the structures in Stancliffe et al. are provided by the weldingof a planar, biaxially heat-shrinkable, plastic mesh layer to a planar,relatively non-heat-shrinkable plastic mesh layer at zones which arespaced apart on a generally square grid. Hence, when the heat-shrinkablelayer is heated and shrinks, the non-heat-shrinkable layer assumes agenerally cuspated configuration with the welded points on thenon-heat-shrinkable layer remaining in contact with the heat-shrinkablelayer. This patent does not provide a single layer fabric and issusceptible to failure at the welding points bonding the layerstogether.

Another pyramidal fabric is described in U.S. Pat. Nos. 5,567,087 and5,616,399, owned by the Assignee of record. The fabrics taught in thosepatents are woven from round, monofilament yarns and a description ofsuch fabrics and their manufacture is set forth in the aforementionedpatents, the subject matter of which is incorporated by referenceherein.

Thus, while attempts have been made heretofore to provide a suitablemeans for stabilizing and retaining soil and for reinforcing turf, theart heretofore has not taught variations to pyramidal fabrics whichprovide improved revegetation, erosion protection and water quality onslopes and in channels.

BRIEF SUMMARY OF THE INVENTION

It is therefore; an aspect of the present invention to provide apyramidal fabric which promotes improved revegetation, provides erosionprotection and improved, water quality on slopes.

It is another aspect of the present invention to provide a pyramidalfabric woven from a multi-lobe filament yarn, providing an increase insurface area.

It is yet another aspect of the present invention to provide a methodfor erosion control and revegetation facilitation employing thepyramidal fabric of the present invention.

At least one or more of the foregoing aspects, together with theadvantages thereof over the known art relating to pyramidal fabrics,which shall become apparent from the specification which follows, areaccomplished by the invention as hereinafter described and claimed.

In general, the present invention provides a pyramidal fabric comprisingtwo sets of multi-lobe filament yarns interwoven in substantiallyperpendicular direction to each other, each of the multi-lobe filamentyarns having pre-determined, different heat shrinkage characteristicssuch that, upon heating, the fabric forms a three-dimensional, cuspatedprofile.

The present invention also includes a method of stabilizing soil andreinforcing vegetation comprising the steps of placing athree-dimensional, high-profile woven fabric into soil, wherein thefabric comprises two sets of multi-lobed filament yarns interwoven insubstantially perpendicular direction to each other, each of themulti-lobe filament yarns having pre-determined, different heatshrinkage characteristics such that, upon heating, the fabric forms athree-dimensional, cuspated profile; securing the fabric to the ground;and, distributing soil and seed onto the fabric such that the section ofground is quickly revegetated and thereby protected from furthererosion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view depicting a pyramidal fabric, according tothe present invention;

FIG. 2 is an enlarged section of FIG. 1;

FIG. 3 is a schematic view of the pyramidal fabric of FIG. 1, showingits general configuration;

FIG. 4 is an enlarged sectional view taken substantially along line 4-4in FIG. 3;

FIG. 5 is an enlarged sectional view taken substantially along line 5-5in FIG. 3;

FIG. 6 is a perspective view of a portion of a multi-lobe filament yarn,forming the pyramidal fabrics of the present invention;

FIG. 7 is a cross-sectional view of the multi-lobe filament yarn of FIG.6; and

FIGS. 8-10 are cross-sectional views of alternative multi-lobe filamentyarns, that can be employed to form the pyramidal fabrics of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed toward geotextile fabrics, as setforth in U.S. Pat. Nos. 5,567,087 and 5,616,399, noted hereinabove. Thedifference between the fabrics described in the patents and the presentinvention is that while the former employed round, monofilaments toweave the fabric, the fabrics of the present invention are woven frommulti-lobe filament yarns and are referred to herein as pyramidalfabrics. Such fabrics are used to prevent erosion of exposed surfacesand to facilitate the revegetation of a previously eroded surface.

A geotextile fabric embodying the concepts of the present invention isgenerally indicated by the numeral 10 in the accompanying drawings andincludes two sets of filaments 15W (warp direction) and 15F (filldirection) interwoven in substantially perpendicular directions to eachother. As best shown in FIG. 2, the fibers or filament yarns areinitially, woven into a type of pattern known in the weaving art as a“waffle weave” or “honeycomb” type of woven pattern. This weavingprocedure, which is well known in the art and can be performed onessentially any conventional textile weaving apparatus, produces agenerally planar, single layer fabric with a distinctive look ofadjacent pyramids on one side of the fabric which oppose and are offsetfrom adjacent pyramids on the other side of the fabric.

Importantly, the filament yarns utilized to produce the geotextilefabric of the present invention are biaxially heat shrinkable. That is,upon being heated, the filament yarns will shrink in both directions.However, the amount of heat shrinkage is different for each filamentyarn depending upon its position within the woven fabric. Hence, whenthe woven, initially planar fabric 10 is subjected to heat, as from ahot steam or water bath, the filaments 15W and 15F are shrunkproportionally to the differing levels of heat shrinkage with which eachfilament was provided. Significantly, by arranging the filaments in apredetermined, well-known fashion based upon their level of heatshrinkage, the initially planar geotextile fabric 10 becomes thicker andmore three-dimensional in shape. As seen in FIGS. 4 and 5, the filamentsprovide a zig-zag cross-section and take up a substantially greatervolume than when the fabric is relatively planar. Consequently, athree-dimensional, high-profile woven geotextile fabric is formed asshown in FIG. 1.

Moreover, the distinctive look of the fabric becomes more pronounced.That is, the pyramidal shapes within the fabric become significantlydeeper and more defined. In one embodiment, the thickness of thegeotextile fabric should grow to at least about 0.25 inches (250 mils).It is this thickness as well as other characteristics of this fabricwhich permit its use for soil retention and turf reinforcement. Moregenerally, the thickness of the fabric can grow from about 0.25 inches(250 mils) to about 0.5 inches (500 mils).

For instance, in one embodiment, the fabric of the present invention canhave a tensile strength of at least about 1800 pounds/foot in the warpdirection and at least about 1800 pounds/foot in the filling directionusing the American Society for Testing and Materials (ASTM) StandardTest Method D-6818. In another embodiment, the fabric of the presentinvention can have a tensile strength of at least about 4900 pounds/footin the warp direction and at least about 3600 pounds/foot in the fillingdirection using the same ASTM Test Method, D-6818. In yet anotherembodiment, the fabric has a tensile strength of at least about 4700pounds/foot in the warp direction and at least about 3500 pounds/foot inthe filling direction, again using ASTM Standard Test Method D-6818.

The fabric can have a modulus at 10% elongation of at least about 9,000pounds/foot in the warp direction and at least about 9,000 pounds/footin the filling direction using the same ASTM Test Method, D-6818. Inanother embodiment, the fabric can have a modulus at 10% elongation ofat least about 12,500 pounds/foot in the warp direction and at leastabout 11,000 pounds/foot in the filling direction. In yet anotherembodiment, the fabric can have a modulus at 10% elongation of at leastabout 18,500 pounds/foot in the warp direction and at least about 16,000pounds/foot in the filling direction using the same ASTM Test Method,D-6818.

At this point, it should be noted that the filaments utilized in thegeotextile fabric of the present invention are thermoplasticcross-sectional multi-lobe filament yarns comprising such materials aspolyethylene and polypropylene homopolymers, polyesters, polyphenyleneoxide, certain fluoropolymers, and mixtures thereof. However, it will beunderstood that any materials capable of producing filaments or fiberssuitable for use in the instant fabric of the present invention fallwithin the scope of the present invention and can be determined withoutdeparting from the spirit thereof. In one embodiment, the filaments ofthe present invention are made of polypropylene, polyethylene, hightenacity polyester, or mixtures thereof.

Moreover, before more specifically detailing the operation of thepresent invention, it should be understood that the process for makingthe geotextile fabric is well known in the art. As noted hereinabove,the weaving process can be performed on any conventional textilehandling equipment suitable for producing the fabric of the presentinvention and thus, a “honeycomb” type weave produced from thermoplasticpolymeric yarns is also well-known in the art.

However, it should be understood that no single-layered, homogeneousfabric has been employed for the purposes of the present invention.Importantly, because of the increased thickness of the fabric providedby the shrinkage of the pre-arranged filaments employed therein whensubjected to heat, the subject invention can be utilized in erosioncontrol and veneer cover soil and stability applications.

Current fibers used in the construction of pyramidal fabrics are roundor oval in shape. The filament yarns 15W and 15F of the pyramidal fabric10 of the present invention consist of multi-lobe filament yarns,indicated generally by the numeral 15 in FIG. 6. The fiber 15 ischaracterized herein as multi-point, multi-lobe or multi-dimensional andas depicted in FIG. 7, provides three separate points or edges, 16, 17and 18 and three grooves or channels 19, 20 and 21, between the points.Due to the geometric orientation of the fiber there is an increase insurface area with grooves/channels along the yarn 15. The filament yarns15 provide a minimum of three points but are not limited to three whenviewing a cross-section of the fiber. With reference to FIGS. 8-10 forinstance, alternative filament yarns 30, 40 and 60, respectively aredepicted. Fiber 30 provides four edges or points, 31-34 and fourchannels, 35-38. Fiber 40 provides five edges or points, 41-45 and fivechannels, 46-51. Fiber 60 provides six edges or points, 61-66 and sixchannels, 67-72. For purposes of discussion herein, reference shall bemade to the fiber 15, with the understanding that it is representativeof a fiber having a multipoint, geometric shape and that practice of thepresent invention is not limited to the specific form of fiber havingthree edges and three channels.

The fiber 15 is extruded via a die that forms the multipoint geometricshape. This shape is made in the extrusion process of the fiber. Theunique geometric orientation-multipoint cross-section of the fibercaptures sediment 75, (FIG. 6) and water, which assist in greatervegetation establishment. The sediment and moisture is captured in thegrooves/channels (16/19 etc.) of the fiber, which enhances seedgermination and root establishment. The fiber allows for greater degreeof crimp amplitude due to the geometric orientation of the fiber.Resiliency data showed a 10 percent increase over the standard round oroval monofilament. Increased loft for ease of plant growth is essentialin a pyramidal fabrics functionality. The pyramidal fabric of thepresent invention 10, revealed seed germination improvements of up to1488 percent over the standard and commonly used monofilament fiberpyramidal fabric when tested in an independent third party lab. Inbench-scale shear testing, a partial vegetated plot using the pyramidalfabric 10 revealed at least a 30 percent reduction in soil loss, ascompared to a pyramidal fabric woven from monofilaments.

The fiber 15 is polymer based, such as polyolefins, polyesters,polyamides, and blends thereof, with polypropylene being preferred. Thefiber 15 is extruded through a die that forms the uniquemultidimensional shape, at temperatures in excess of 380.degree. to 440°F., (193° to 227° C.), which provides the multipoint cross-sectionalfiber. The fiber is extruded through a water quench bath at temperaturesof 70° C. The fiber is then pulled through several blowers and dryers toremove the excess water from the channels of the fiber. The fiber isthen drawn into the oven at temperatures of 280+%31 15° C. and drawratio of 6.0/1 to 8.0/1.

Each fiber is one continuous strand (minimum of 160 holes per die) whichis wound up on a winder to form a package or spool. Deniers of the fiber15 range from about 300 (333 decitex) to about 2000 (2222 decitex) withfrom about 500 (555 decitex) to about 1100 (1222 decitex) beingpreferred, irrespective of the actual cross-sectional geometry. It is tobe appreciated that the drawings depict an idealized multipointcross-section for the fibers, where each edge or lobe, e.g., 16, 17, 18,and channel e.g., 19, 20 and 21, is uniform. In reality, the edges andchannels are not symmetrical or sharply defined, as a result ofquenching; however, the filament yarns do have distinct edges andchannels, so as to provide a multi-dimensional geometry.

Specific embodiments of the present invention involve methods forpreventing erosion control or promotion of revegetation of a barren orpreviously eroded area, or both. It is believed that the increasedsurface area of the multi-lobe filament yarns of the present inventionprovide a great surface area on which runoff water can drain withoutdamaging, i.e., eroding, the underlying soil. Further, the irregularlyshaped voids of the present pyramidal fabric provide ample space intowhich sediment, soil and seed, if any, can fall, thereby holding downthe fabric as well as facilitating its incorporation into/onto thesurface to be protected.

For example, the present invention includes a method of stabilizing soiland reinforcing vegetation comprising the step of placing athree-dimensional, high-profile woven fabric into soil, wherein thefabric comprises two sets of multi-lobe filament yarns interwoven insubstantially perpendicular direction to each other, each of themulti-lobe filament yarns having predetermined, different heat shrinkagecharacteristics such that, upon heating, the fabric forms athree-dimensional, cuspated profile; securing the fabric to the ground;and, distributing soil and seed onto the fabric such that the section ofground is quickly revegetated and thereby protected from furthererosion.

The fabric can be secured to the ground by U-shaped wire staples ormetal Geotextile pins. Wire staples should be a minimum thickness of 8gauge (4.3 mm). Metal pins should be at least 3/16 in (4.7 mm) diametersteel with a 1.5 in (38 mm) steel washer at the head of the pin. Wirestaples and metal pins should be driven flush to the soil surface.Depending on slope the number of staples or pins range from 1 to 3 persquare yard. Prior to installing one must grade and compact the area ofinstallation and remove rocks, clods, vegetation or other obstructionsso that the installed mat will have direct contact with soil surface.Prepare seedbed by loosening 2 to 3 inches (50-75 mm) of topsoil abovefinal grade. Incorporate amendments such as lime and fertilizer intosoil if needed. Seed are applied to the soil surface before installingmat or after installation.

A series of performance-related index tests have been developed by theErosion Control Technology Council (ECTC) to make rolled erosion controlproduct (RECP) testing more cost-effective and time-efficient. Using theturf reinforcement mats of the present invention as RECP's, thesetesting methods were employed for RECP characterization tests whichdemonstrates efficacy of the invention. First, a brief background onRECP characterization, is provided as follows.

Soil Loss and The Soil Loss Ratio. When used on slopes, the primaryconsideration of RECP systems is their ability to reduce soil losscaused by raid and immediate runoff. Soil loss, ratio is equal to thereduction in soil loss when using a specific RECP system compared to thecomparable bare soil (control) condition.

Permissible Shear Design. Flowing water in channels imposes shear stresson the sides and bottom of the channel. In the permissible shear stressof an RECP used to line the channel is greater than the imposed shear,the lining is considered to provide acceptable erosion resistance.

Mulching and RECP Longevity. RECPs often are used to provide short-termmulching, along with erosion protection, aimed at nurturing vegetationgrowth. As a result, there is a need to evaluate the effectiveness of anRECP in nurturing initial seed germination. Additionally, vegetation mayrequire varying times to develop sufficiently to provide significanterosion protective cover. Times may range from 6 weeks in, humidenvironments to several years in arid conditions. Some RECPs arerequired to provide permanent turf reinforcement. In all cases the RECPmust be shown to have the appropriate longevity.

Testing Approach

ECTC's Slope Erosion Test. The ECTC test method titled, “Standard IndexTest Method for the Determination of Unvegetated Rolled Erosion ControlProduct (RECP) Ability to Protect Soil from Rain Splash and AssociatedRunoff Under Bench-Scale Conditions” establishes the procedures forevaluating the ability of Rolled Erosion Control Products (RECPs) toprotect soils from rain splash and immediate runoff-induced erosion. Thecritical element of protection measured is the ability of the RECP toabsorb the impact force of raindrops, thereby reducing soil particleloosening through “splash” mechanisms. The test method utilizes alaboratory-scale testing apparatus, rather than full-scale fieldsimulation.

ECTC's Channel Erosion Test. The ECTC test method titled, “StandardIndex Test Method for Determination of Unvegetated Rolled ErosionControl Product (RECP) Ability to Protect Soil fromHydraulically-Induced Shear Stresses Under Bench-Scale Conditions”establishes the procedures for evaluating the ability of Rolled ErosionControl Products (RECPs) to protect soils from flow-induced erosion. Thetest method utilizes a laboratory-scale testing apparatus, rather thanfull-scale field simulation.

ECTC's Mulching Test. The test method titled, “Standard Index TestMethod for Determination of Temporary Degradable Rolled Erosion ControlProduct (RECP) Performance in Encouraging Seed Germination and PlantGrowth” establishes the procedures for evaluating the ability of RECP'sto encourage seed germination and initial plant growth. The results ofthe test can be used to compare RECPs and other erosion control methodsto determine which are the most effective at encouraging the growth ofvegetation in different climates.

Summary of Test Results

The following ASTM tests were conducted using Samples A and B. Sample Awas an existing pyramidal fabric, employing round monofilament fibersfor the non-woven mat. Sample B was a pyramidal fabric of the presentinvention, employing multi-lobe filament yams. For a control, nopyramidal fabric was employed over the soil. Each test provides aphysical property e.g. tensile strength, first for an A sample, followedby a B sample. Tests results have been reported in Tables I through III.Tensile testing, reported in Table I, was conducted according to ASTM D6818 and resiliency was conducted according to ASTM D 6524. Germinationtesting was reported in Table II and Bench-Scale shear testing wasreported in Table III.

The Bench-Scale shear testing employs the following apparatus andprocedures. 8 inch (20.3 cm) diameter, 4 inch (10.2 cm) deep potscontaining RECP-protected soil are immersed in water, and the surface issubjected to shear stresses caused by the rotation of an impeller for 30minutes. The shear stress test apparatus includes a tank, an internal“table” to hold recessed pots, and an impeller. The impeller is mountedin the cylindrical tank so that the lower edge of the blades is slightlyabove the surface of the pots. The internal table has openings that holdthe pots of soil. When pots are placed in the table openings, the testsurface is flush with the top of the table. The amount of soil thaterodes is found from weighing the containers of saturated soil bothbefore and after testing. Tests are commonly run at multiple (at leastthree) shear stress levels. From this data the shear stress associatedwith a critical amount of soil loss (typically 0.5 in (1.25 cm)) can becalculated. The critical shear stress is sometimes referred to as the“permissible shear stress” of the RECP.

Shear, where X=Shear stress (lb/ft2), is calculated using the followingdata:

y=Unit weight of water (lb/ft3)

y=Flow depth (ft)

2f=Angle of energy grade line (degrees)

x=y*ŷ*2f.

TABLE I Comparative Evaluation of Pyramidal Fabrics CurrentSpecification % difference Property Me Units MARV^(a) Fabric A Fabric Bto Std Data Thickness MD mils 500 409 393 −4% Mass Per Unit Area MDoz/yd² 14 15.11 13.69 −9% Resiliency MD % change −20 −7.1 −11.3 59%Flexibility MD mg-cm N/A 726532 610969 −16%  Tensile Strength-MD MDlb/ft 3200 4752 4560 −4% Tensile Strength-XMD lb/ft 2200 3192 3468  9%Tensile Elongation-MD MD % 65 (MAX) 42 50.7 21% Tensile Elongation-XMD %65 (MAX) 38.7 36 −7% Light Penetration MD % 25 13.5 6.6 −51%  GroundCover % 75 86.5 93.4  8% ^(a)Minimum average roll value

TABLE II Germination Testing Fab- Fab- % difference Property Units daycontrol ric A ric B to Std Data Seeds Germinated # per 4 0 0 0 0 n/a perarea in² area 7 0 0 0 n/a 14 2.6 0 4.4 n/a 21 8.2 0.8 12.7 1488% AveragePlant inch 0 0 0 0 n/a Height 7 0 0 0 n/a 14 1.4 0 1.4 n/a 21 1.6 1 1.5 50% Plant mass mg 21 3.9 1 8.6  760% per area per 4 in²

With reference to the data, after 21 days, the Sample B product showed a1488% improvement over the Sample A product for seed germinated perarea. For average plant height, the improvement of Sample B over SampleA was 50% and for plant mass per area, the improvement of Sample B overSample A was 760%. Generally, using the fabrics according to the presentinvention, seed germinated per area provides at least a 50% improvementover fabrics made with round monofilaments; likewise for average plantheight, the improvement is from about 30% to about 50% for fabrics ofthe present invention, respectively and, for plant mass per area, theimprovement is from about 350% to about 760% for two fabrics of thepresent invention.

TABLE III Bench-Scale Shear Testing % difference psf Fabric A Fabric Bto Std Data 3.87 413 288 −30% 4.72 590 370 −37% 5.57 683 432 −37%

In Table III, the water flow is designated as pounds per square foot(psf), in the first column. Soil lost by washing, measured in grams, islisted for Fabrics A and B in the next two columns. By interpolationfrom the lab scale testing, a loss of 450 grams of soil is equivalent toone-half inch (1.25 cm) in the field and is unacceptable. The results ofTable III indicate that Sample B had 30% less soil loss than Sample A at3.87 psf and 4.72 psf and 37% less soil loss than Sample A at 5.57 psf.In no instance did Fabric B lose 450 grams of soil.

Using the fabrics of the present invention, soil losses can be reducedby at least about 30%, compared to pyramidal fabrics constructed ofround monofilaments.

Pyramidal fabric of the present invention (Sample B) was also evaluatedagainst traditional round monofilament yarn pyramidal fabric (Sample A)in vegetation tests, as reported in Table IV.

TABLE IV Pyramidal Fabric Tested with Standard Kentucky BluegrassVegetation Unit of Traditional Measure Round Multi-Lobe PerformanceImprovement of Shear Stress Lb/ft² 10.1 13.3 32% Velocity Ft./sec. 1517.9 19% Decrease Growing Time Planted June 1999 June 2004 Tested June2000 Mid-September 2004 Duration Months 12 3.5 −71% 

With reference to Table IV, it can be seen shear stress and velocitywere both improved for the pyramidal fabrics of the present invention.Additionally, growing time was decreased significantly by the use of thepyramidal fabrics of the present invention. Using the pyramidal fabricsof the present invention, decreased growing times of at least about 50%can be obtained as compared to pyramidal fabrics made from traditionalround yarns.

Thus, it should be evident that the pyramidal fabrics and method of thepresent invention are highly effective in preventing erosion fromexposed surfaces and promoting revegetation of previously erodedsurfaces. The invention is particularly suited for erosion control andpromotion of revegetation of a previously eroded land surface, but isnecessarily limited thereto.

Based upon the foregoing disclosure, it should now be apparent that theuse of the pyramidal fabrics described herein will carry out the objectsset forth hereinabove. It is, therefore, to be understood that anyvariations evident fall within the scope of the claimed invention andthus, the selection of specific component elements can be determinedwithout departing from the spirit of the invention herein disclosed anddescribed. In particular, multi-lobe filament yarns according to thepresent invention are not necessarily limited to those having atri-lobal cross section. Thus, the scope of the invention shall includeall modifications and variations that may fall within the scope of theattached claims.

1-16. (canceled)
 17. A three-dimensional, single-layered, geotextile matcomprising woven drawn, trilobal, heat-shrinkable, thermoplastic polymerfilament yarns comprising a denier in the range of about 1200 to about2000 having a cuspated conformation on both an upper face of thegeotextile mat and a lower face of the geotextile mat wherein the upperand lower faces of the mat comprise the same composition.
 18. Thegeotextile mat of claim 17 comprising a waffle weave pattern.
 19. Thegeotextile mat of claim 17 comprising a honeycomb weave pattern.
 20. Thegeotextile mat of claim 17 wherein each trilobal filament yarnscomprises different heat shrinkage characteristics depending upon itsposition within the woven mat.
 21. The geotextile mat of claim 17wherein the cuspated conformation comprises pyramidal shapes.
 22. Thegeotextile mat of claim 17 wherein the drawn, trilobal, thermoplasticpolymer, filament yarn includes a cross-sectional geometry having a coreregion and three substantially curved lobes and three channels.
 23. Thegeotextile mat of claim 22 wherein the trilobal filament yarns comprisea thermoplastic polymer selected from the group consisting ofpolyethylene, polypropylene, polyester, polyphenylene oxide, andmixtures thereof.
 24. The geotextile mat of claim 17 wherein thetrilobal filament yarns comprise a polyolefin.
 25. The geotextile mat ofclaim 17 wherein the trilobal filament yarns comprise a polyamide. 26.The geotextile mat of claim 17 wherein the trilobal filament yarnscomprise a fluoropolymer.
 27. The geotextile mat of claim 17 wherein thetrilobal filament yarns comprise a blend of at least two of thepolymers.
 28. The geotextile mat of claim 17 the drawn, trilobal,thermoplastic polymer, filament yarn includes a cross-sectional geometryhaving a core region and three nonsymmetrical lobes and three channels.29. The geotextile mat of claim 17 wherein the trilobal filament yarnsare biaxially heat shrinkable.
 30. The geotextile mat of claim 17wherein the trilobal filament yarns comprise a cross-sectional geometryhaving a core region and three nonsymmetrical lobes and threenonsymmetrical channels.
 31. The geotextile mat of claim 17 wherein thesingle layer woven mat having a cuspated conformation is heated toproduce differing levels of shrinkage in the trilobal filament yarns,which is dependent upon each yarn's individual position within thesingle layer woven mat.
 32. The geotextile mat of claim 17 comprising athickness in the range of about 0.25 inches (250 mils) to about 0.5inches (500 mils).
 33. The geotextile mat of claim 17 comprising amodulus at 10% elongation of at least about 9000 pounds/foot in the warpdirection and about 9000 pounds/foot in the filling direction.
 34. Thegeotextile mat of claim 17 comprising a tensile strength in the warpdirection of about 1800 pounds/foot and about 1800 pounds/foot in thefilling direction.
 35. The geotextile mat of claim 17 wherein thetrilobal filament yarns comprise a cross-sectional geometry having acore region and three nonuniform lobes and three nonuniform channels.